The concept of a house needing to breath is greatly misapplied! Though the structure needs to breath to a certain extent, it does not, and should not, apply to the interior living air breathing into the structure. That concept is a myth! Indoor air quality is NOT an insulation issue. I live & work in one of the most severe climates in the country & I get called on to fix the problems created by this myth way too much.
An Energy efficient house needs to be as tight as possible. There is no such thing as too tight. However, on a tight house, management of indoor air needs to be handled.